Generally, spacing is determined by the age of the tree. Recommended
spacing today is to use the square system and plant on a 45 foot center.
These trees will have to be thinned by age 20-25 years.

Proper spacing is desirable to eliminate competition for nutrients,
moisture, and sunlight. Ideally, the tree limbs should never overlap.
At mid-day during the summer, 25-35 percent of the ground should receive
sunlight.